From: Phrogz <phrogz@...>
Date: 2007-09-24T13:25:08+09:00
Subject: Re: Nested array filling bad..

On Sep 23, 8:08 am, Josselin <josse...@wanadoo.fr> wrote:
> irb(main):001:0> cat_a = Array.new(7, Array.new)
> irb(main):002:0> cat_a[0] << 0
> => [0]
> irb(main):004:0> cat_a[1] << 1
> => [0, 1]
>
> but it gives me back
> irb(main):005:0> cat_a
> => [[0, 1], [0, 1], [0, 1], [0, 1], [0, 1], [0, 1], [0, 1]]
>
> I would like to get back
>
> [ [0], [1], [], [], [], [], [] ]

irb(main):001:0> cat_a = Array.new(7){ [] }
=> [[], [], [], [], [], [], []]
irb(main):002:0> cat_a[0] << 0
=> [0]
irb(main):003:0> cat_a[1] << 1
=> [1]
irb(main):004:0> cat_a
=> [[0], [1], [], [], [], [], []]


What's wrong with it is that you are using the exact same array for
all 7 spots. You want a new Array to be created for each spot, using
the block notation above.